Node.js MongoDB Update doesn't work

I'm new in MongoDB and i am trying to use it in Node.js.

I'm having a problem in doing an update of a specific document. I don't get any error but it don't update the data in the collection.

Can anyone tell me what i'm i doing wrong?

app.post("/update", function(req,res)
{
    var query   = req.query;
    var code    = query.code;       

    var db      = req.db;
    var data    = db.get("data");

    data.update( 
        { 
            code : code         
        },
        {   
            course : req.body.course,
            grade  : req.body.grade,
            year   : req.body.year,
            code   : req.body.code              
        },
         function (err, result) {
            if (err) console.log("erro:" + err);
                console.log("result" + result);
         }
    );
});

Thanks